Recent guidelines by Schwartz and colleagues (2017 PMID 28045591) note that removal of the earwax should result in resolution of symptoms:
Clinicians should assess patients at the conclusion of in-office treatment of cerumen impaction and document the resolution of impaction. If the impaction is not resolved, the clinician should use additional treatment. If full or partial symptoms persist despite resolution of impaction, the clinician should evaluate the patient for alternative diagnoses.
In an interesting study by Lewis-Cullinan and Janken (1990 PMID 2358577), the authors assess geriatric patients for earwax buildup that they were unaware of.
On either the second or third day of hospital stay, subjects were given a hearing test using an AudioScope and then their ear canals were examined for impacted cerumen. Ear canal irrigations were performed on those subjects with impacted cerumen. All subjects received a second hearing test. ... A significant interaction (F = 146.83, d.f. = 2/223, P less than 0.0001) between hearing tests and cerumen removal was found indicating that those with no occlusion had no change in hearing whereas both occluded groups increased with the greatest change for the bilateral group.
In other words, patients who had no idea they had hearing loss had their ear wax removed and had resolution by the next day.